First i would offer your son the money NOT to marry this girl.
Seems to me she isnt very thoughtful or considerate of anyone else's feelings but her own. I am almost 40, married 15 years and we paid for my dream wedding ourselves. Our parents gave us a gift of what they could afford and no feelings were hurt.If she wants to get all traditional on you. HA! then the jokes on her, the brides family pays for most and they even should pay your family for marrying their selfish daughter.

goodluck to you i have a feeling your gonna need it with this girl.